A light emitting diode (LED) is a semiconductor device constituted mainly by group III-V compound semiconductor materials, for instance. Such semiconductor materials have a characteristic of converting electricity into light. Hence, when a current is applied to the semiconductor materials, electrons therein would be combined with holes and release excessive energy in a form of light, thereby achieving an effect of luminosity.
Generally speaking, since the nitride-based material served as an active-layer material in the LED has direct bandgap (Eg) from the deep ultraviolet (UV) waveband to the far-infrared waveband (6.2 eV to 0.7 eV), the nitride-based material in the conventional technique fabricated the LED with wavelengths ranging from green to ultraviolet, so as to be characterized by high internal quantum efficiency (IQE). Conventionally, in order to enhance the carrier confinement effects, one electron barrier layer is formed after the growth of the quantum barrier layer closest to the p-type semiconductor layer, so as to enhance the overall luminous intensity of the LED. However, the mismatch phenomenon of the polarization field is caused due to the difference in the lattice constants between the electron barrier layer and the quantum barrier layer closest to the p-type semiconductor layer, and thus fine carrier confinement effects can not be achieved and the hole injection efficiency is reduced, thereby decreasing the luminous efficiency. As a result, manufacturers in the pertinent art endeavour to develop LED with satisfactory luminous efficiency.